In conventional refrigerating apparatuses using single refrigerant such as R22, the charging of refrigerant into refrigerant circuitry is executed in the following manner, as disclosed in "Shinban Dai-4-Han, Reito-Kucho Binran (Kiso-Hen)", pp.704-705, edited by Japan Society of Refrigerating and Air Conditioning Engineering.
Specifically, first, a refrigerant cylinder is connected through a tube to a refrigerant charge valve of the refrigerant circuitry previously maintained under vacuum. Then, the refrigerant charge valve is opened to let refrigerant in the refrigerant cylinder flow into the refrigerant circuitry due to the pressure difference between the insides of the refrigerant cylinder and the refrigerant circuitry.
As the refrigerant is charged into the refrigerant circuitry, the pressure in the refrigerant circuitry is increased. Therefore, the pressure difference between the insides of the refrigerant cylinder and the refrigerant circuitry becomes gradually lessened so that the charging speed of refrigerant is gradually reduced. In particular, when the air temperature at the outdoors where the refrigerant cylinder is put, i.e., the open-air temperature, is low, the pressure in the refrigerant cylinder is low and therefore the pressure difference readily becomes lessened.
Accordingly, the amount of refrigerant charged into the refrigerant circuitry per unit time is decreased. As a result, the charging speed of refrigerant becomes extremely slow in a short time. In other words, even though the pressure in the refrigerant cylinder is higher than that in the refrigerant circuitry, there arises a condition that substantially little refrigerant can be charged into the refrigerant circuitry.
If such a condition arises, the following measures are generally taken in order to increase the charging speed of refrigerant.
Specifically, the refrigerant cylinder is connected to a valve provided in the line on the suction side of a compressor. And, refrigerant is supplied to the refrigerant circuitry through the valve with the compressor operated. In this manner, a large pressure difference is ensured between the insides of the refrigerant circuitry and the refrigerant cylinder, thereby increasing the charging speed of refrigerant.